358 Prof. A. E. Verrill on the Affinities of Pakeozoic 



notwithstanding the great amount of evidence that has been 

 published to show that the " Tabulata " include corals very 

 diverse in structure and affinities. The proposition of Pro- 

 fessor Agassiz to regard all " Tabulate " and " Rugose " 

 corals as Acalephs has not been very generally adopted, but 

 has been received with more or less hesitation and doubt by 

 many zoologists and geologists. In fact it is not easy to see 

 how Professor Agassiz could reconcile, in his own mind, the 

 structure of many of the Tabulata and Rugosa with his own 

 definitions of the two classes Polyps and Acalephs. The di- 

 stinction upon which he and others have chiefly insisted is the 

 existence in the former of radiating fleshy lamellae, dividing 

 the interior of the body into a number of radiating chambers, 

 in the centre of which, in coral-making species, the radiating 

 plates are formed ; while in Acalephs no such radiating 

 lamellae and chambers exist. Therefore it would not be pos- 

 sible for an Acaleph to form a coral having distinct radiating 

 plates or septa, unless we alter om' definition of an Acaleph. 

 In that case I do not know what distinction would remain. 

 And yet we find many Tabulate corals, both recent and ancient, 

 with twelve or even twenty-four well-developed radiating 

 septa ; and among the Rugosa there are very many genera in 

 which numerous radiating septa are as highly developed as in 

 the ordinary modern corals of undoubted polyp-origin, while 

 in some there are not even traces of transverse septa. If we 

 regard the relations of the soft jjarts to the corals, it will 

 therefore be necessary to consider all corals in which distinct 

 radiating plates are formed as true polyp-corals ; but the 

 absence of such plates is not of itself proof that the coral was 

 not made by a polyp ; for many corals now living, and formed 

 by genuine polyps, have no radiating septa (e. g. Tuhijpora^ 

 some species oi Pocillopora). 



In the present state of science, the only stony corals which 

 are known to be formed by hydroids are the several species of 

 Mille'pora. We can reasonably infer that a few other genera 

 having essentially the same structure, or belonging properly to 

 the same family, are also the corals of Hydroids. But as to the 

 great majority of the " Tabulata" and " Rugosa," there can 

 no longer be any reasonable doubt that they were made by true 

 polyps, essentially similar to those of the existing corals *. 



* The following quotation from tlie * Bulletin of the Mus. of Comp. 

 Zoology,' vol. i. no. 13, p. 384, Nov. 1869, will serve to illustrate the views 

 of Professor Agassiz : — 



"If we now remember that the Acalephian affinities of the Tabulata 

 are unquestionable, and tliat, with them, the Rugosa must be removed 

 from the class of Polyps and referred to that of the Acalephs, and if we 

 further take into consideration the fact that Palceudiscus belongs to the 



